The correct answer is C. Spanish rode horses, had European diseases.
How were the Aztecs and Incas easily defeated by the Spanish?
Spanish conquistadors, including figures like Hernán Cortés (involved in the conquest of the Aztecs) and Francisco Pizarro (involved in the conquest of the Incas), did ride horses and used military advantages like large dogs, but the impact of diseases on the native populations was profound.
The lack of immunity to these diseases among the Aztecs and Incas resulted in widespread epidemics and contributed significantly to the ease with which the Spanish were able to conquer these civilizations.